How it works is that you add only apps/packages that you want to appear in Installer instead of ALL the apps/packages from Community Sources and/or elsewhere. The beauty of it is that your personalized source will stay sync'd as it grabs updates from the actual repositories.

Find the apps/packages that you want to add to your personal repository by either searching or by going through the categories (ala Installer-style) on the left side menu and then clicking on Add Package button on the top-right corner of the package listing to add it to your personal repository.

If you want to remove a package that you added, just click on the Remove Package.